A fan motor used in a vehicle for air-conditioning needs to be compact and produce a large volume of airflow. To achieve these targets, a fan motor and a blower are disclosed in Unexamined Japanese Patent Application Publication No. H07-144528 (Patent Literature 1). The fan motor and the blower disclosed can operate more efficiently, and produce lower noises, and be downsized. Such a conventional fan motor as disclosed in Patent Literature 1 includes a double-sided shaft, i.e. the shaft extends through the motor to both sides and a fan is respectively put on both sides of the shaft to form a double-fan structure. For instance, as shown in patent literature 1, a centrifugal fan shaped cylindrically is put on both sides of the shaft for the blower to suck air, and the air is discharged along one direction. This structure allows the blower to suck a greater volume of air and achieve a higher sucking efficiency than a single-side fan structure where the fan is mounted on a single side of the shaft. On top of that, since the fan is mounted on both sides of the shaft respectively, the fans can operate in well-balanced manner than the fan mounted on a single side of the shaft, and lower noises can be thus achievable.
Unexamined Japanese Patent Publication No. 2001-37133 (Patent Literature 2) discloses a technique on a brushless motor which includes a stator with toroidal windings, an inside rotor and an outside rotor. This structure employed in a conventional brushless motor allows reducing a volume of the coil end, lowering the copper loss while outputting greater torque.
The double-fan structure discussed above basically places a motor between the two fans, so that when the width of the motor is great along the rotary shaft of the motor, the fans are obliged to reduce their widths. A narrower width of the fan will reduce the cubic volume of the fan, and thus the airflow quantity decreases. To obtain a sufficient airflow quantity, the width of the motor along the rotary shaft should be reduced.